Pasture digestion in response to change in ruminal pH
M.J. De Veth and E.S. Kolver
Dairying Research Corporation, Private Bag 3123, Hamilton, New
Zealand.
Proceedings of the New Zealand Society of Animal Production. 1999, 59: 66-69
Four continuous culture fermenters were used to determine the
ruminal pH required for the optimal digestion of pasture. Spring pasture
was fermented at four controlled levels of ruminal pH (5.4, 5.8, 6.2 and
6.6) according to a 4x4 Latin square design. Decreasing pH from 6.6 to
5.4 reduced dry matter digestion by 14%, neutral detergent fibre
digestion by 11%, total non-structural carbohydrate digestion by 5% and
microbial nitrogen flow by 18%. A quadratic relationship was observed
between ruminal pH and the true ruminal digestibility of dry matter
(R²=0.94, SE=2.06) and microbial nitrogen flow (R²=0.66,
SE=0.05).
The ruminal digestibility of pasture dry matter was optimised at pH
6.35, and synthesis of microbial protein was optimised at pH 6.13. This
experiment indicated that digestion was largely insensitive to pH across
a broad range of pH (5.8 to 6.6), but that a large reduction in
digestion occurred when mean pH was less than 5.8.
Keywords: NZSAPAB;
Pasture; rumen; pH; microbial protein synthesis; continuous
culture.
Last Updated 06-08-1999
